Electroplating is a manufacturing technique used in the fabrication of head suspension components or other components with conductive (commonly metal or metal alloy) layers. This technique involves the passage of plating current through an electrolytic solution containing metal ions between two electrodes of a plating power supply (e.g. a battery). The plating current causes an electrochemical reaction on the surface of an electroplating panel having strips of components to be electroplated. This reaction results in deposition of an electroplated metal layer on the surfaces of the components through which the plating current is passed. Generally, in the electroplating process, the thickness profile of the electroplated metal layer is controlled to be as uniform as possible. It is advantageous for the electroplated metal layer to have a uniform or flat thickness profile across the surfaces of the components.
Nevertheless, the conventional electroplating techniques are susceptible to relatively non-uniform thickness profile variations. Such variations are due to relatively non-uniform plating current distribution over the surfaces of the components.
FIG. 1 is a schematic view of a prior art electroplating panel 30 having several strips 32 of components 34 to be electroplated. FIG. 1 primarily shows electrical features (e.g. the conductive metal) of the electroplating panel 30. Each strip 32 of the components 34 extends between the opposite borders 40 of the panel 30. Each strip 32 also includes an edge portion 36 extending between the opposite borders 40. The components 34 are spaced apart from one another along the edge portion 36.
The panel 30 further includes a main buss 38 extending along the opposite borders 40 of the panel. Each strip 32 has an associated strip buss 42 extending along the edge portion 36 of the strip 32. The strip buss 42 has two opposite ends 44 and 46 electrically connected to the main buss 38, respectively. The strip busses 42 are also electrically connected to each of the components 34 to be electroplated on the associated strip 32.
During the electroplating process, the panel 30 is immersed into an electrolytic solution. When a voltage is applied from a plating power supply, the plating current flows through the electrolytic solution and the panel 30. The amount of metal plated on the components 34 depends on the distribution of plating current density on each strip 32 of the panel 30.
In the illustrated prior art embodiment, the ohmic resistance of the strip buss 42 and the components 34 on the strip 32 gradually increases from the opposite ends 44 and 46 toward the middle point 33 of the strip buss 42. Such resistance contributes to plating current density drop from the opposite ends 44 and 46 to the middle point 33 of the strip buss 42. Consequently, the plating current density on the strip 32 varies somewhat (i.e. tends to be higher at two opposite ends 43 and 45 of the strip 32). As a result, the plating rate tends to be substantially greater at the opposite ends 43 and 45 of the strip 32 relative to the interior of the strip 32. Because of this relatively non-uniform plating rate, the final electroplated metal layer on the strip 32 tends to have a “dish” type pattern (i.e. thicker at the opposite ends 43 and 45 of the strip 32 and thinner at the center of the strip 32).
There are two electrical contacts on each panel. If a strip on the panel is closer to the electrical contacts than other strips, the electroplated metal layer on this strip tends to have a thicker “dish” type pattern. The electroplated metal layer on the strip that is closest to the electrical contacts tends to have the thickest “dish” type pattern.
It would be desirable to control the thickness profile of the electroplated metal layer to compensate for the relative non-uniformity that can arise in the electroplating process. A number of electroplating devices and methods directed to improvements of plating thickness distribution are described, for example, in U.S. Pat. Nos. 3,862,891, 3,880,725, 4,534,832, 5,443,707, 5,788,829, 5,804,052, 6,027,631, 6,033,540, 6,210,554, 6,261,426, and 6,267,860 as well as in U.S. Pub. Nos. 2001/0054556 and 2002/0079230. However, there is a continuing need for apparatus and methods that can control the thickness of the electroplated metal layer to a desired profile of uniformity in panels having strips of components.